This invention relates to metal cyanide complexes. More particularly, it relates to metal cyanide catalysts having specific complexing agents, to heterogeneous metal cyanide catalysts, and to methods for polymerizing alkylene oxides in the presence of a metal cyanide catalyst.
Polyethers are prepared in large commercial quantities through the polymerization of alkylene oxides such as propylene oxide and ethylene oxide. The polymerization is usually conducted in the presence of an initiator compound and a catalyst. The initiator compound usually determines the functionality (number of hydroxyl groups per molecule) of the polymer and in some instances incorporates some desired functional groups into the product. The catalyst is used to provide an economical rate of polymerization.
Metal cyanide complexes are becoming increasingly important alkylene oxide polymerization catalysts. These complexes are often referred to as xe2x80x9cdouble metal cyanidexe2x80x9d or xe2x80x9cDMCxe2x80x9d catalysts, and are the subject of a number of patents. Those patents include, for example, U. S. Pat. Nos. 3,278,457, 3,278,458, 3,278,459, 3,404,109, 3,427,256, 3,427,334, 3,427,335 and 5,470,813, among many others. In some instances, these metal cyanide complexes provide the benefit of fast polymerization rates and narrow polydispersities. Additionally, these catalysts sometimes are associated with the production of polyethers having very low levels of monofunctional unsaturated compounds.
The most common of these metal cyanide complexes, zinc hexacyano-cobaltate (together with the proper complexing agent and an amount of a poly(propylene oxide)), has the advantages of being active and of forming poly(propylene oxide) having very low unsaturation. However, the catalyst is quite difficult to remove from the product polyether. Because of this difficulty, and because the catalyst can be used in small amounts, the usual practice is to simply leave the catalyst in the product. However, this means that the catalyst must be replaced. In addition, the presence of the residual catalyst in the polyether product has been reported to cause certain performance problems. These include poor storage stability and, in some instances, interference with downstream processes. In order to reduce catalyst expense and to avoid these problems, it would be desirable to provide a catalyst that can be recovered easily from the product polyether.
In one aspect, this invention is a water insoluble metal cyanide catalyst that is complexed with a silane-functional complexing agent.
In a second aspect, this invention is an organosilicone polymer having pendant heteroatom-containing groups that are complexed with a water insoluble metal cyanide catalyst.
In a third aspect, this invention is a supported catalyst complex comprising a water-insoluble metal cyanide coupled to a support through a silane coupling agent containing a heteroatom-containing functional group that is complexed with said metal cyanide.
In a fourth aspect, this invention is a supported catalyst comprising a support having coated thereon a polymer containing repeating units derived from a complex of a water insoluble metal cyanide and a silane-functional complexing agent.
In a fifth aspect, this invention is a method of polymerizing an alkylene oxide, comprising contacting said alkylene oxide with an initiator compound under polymerization conditions with a polymer containing repeating units derived from a complex of a water insoluble metal cyanide and a silane-functional complexing agent.
The complex of the invention includes a water insoluble metal cyanide catalyst. These metal cyanide catalysts are well known, and are often referred to as xe2x80x9cdouble metal cyanidexe2x80x9d or xe2x80x9cMCxe2x80x9d catalysts because in most instances these complexes include two different metal ions. The metal cyanide catalysts can be represented by the general formula
Mb[M1(CN)r(X)t]c[M2(X)6]d.nM3xAy,
wherein M is a metal ion that forms an insoluble precipitate with the M1(CN)r(X)t group and which has at least one salt which is soluble in water or an organic compound as described below;
M1 and M2 are transition metal ions that may be the same or different;
each X independently represents a group other than cyanide that coordinates with an M1 or M2 ion;
M3xAy represents a salt of metal ion M3 and anion A which is soluble in water or an organic compound as described below, wherein M3 is the same as or different than M;
b and c are positive numbers that, together with d, reflect an electrostatically neutral complex;
d is zero or a positive number;
x and y are numbers that reflect an electrostatically neutral salt;
r is from 4 to 6; t is from 0 to 2; and
n is a positive number (which may be a fraction) indicating the relative quantity of M3xAy.
The X groups in any M2(X)6 do not have to be all the same. The molar ratio of c:d is advantageously from about 100:0 to about 20:80, more preferably from about 100:0 to about 50:50, and even more preferably from about 100:0 to about 80:20.
The term xe2x80x9cmetal saltxe2x80x9d is used herein to refer to a salt of the formula MxAy or M3xAy, where M, M3, x, A and y are as defined above.
M and M3 are preferably metal ions selected from the group consisting of Zn+2, Fe+2, Co+2, Ni+2, Mo+4, Mo+6, Al+3, V+4, V+5, Sr+2, W+4, W+6, Mn+2, Sn+2, Sn+4, Pb+2, Cu+2, La+2 and Cr+3. M and M3 are more preferably Zn+2, Fe+2, Co+2, Ni+2, La+3 and Cr+3. M is most preferably Zn+2.
M1 and M2 are preferably Fe+3, Fe+2, Co+3, Co+2, Cr+2, Cr+3, Mn+2, Mn+3, Ir+3, Ni+2, Rh+3, Ru+2, V+4 and V+5. Among the foregoing, those in the plus-three oxidation state are more preferred. Co+3 and Fe+3 are even more preferred and Co+3 is most preferred. M1 and M2 may be the same or different.
Preferred groups X include anions such as halide (especially chloride), hydroxide, sulfate, carbonate, oxalate, thiocyanate, isocyanate, isothiocyanate, C1-4 carboxylate and nitrite (NO2xe2x80x94), and uncharged species such as CO, H2O and NO. Particularly preferred groups X are NO, NO2xe2x80x94 and CO.
r is preferably 5 or 6, most preferably 6 and t is preferably 0 or 1, most preferably 0. In many cases, r+t will equal six.
Suitable anions A include halides such as chloride and bromide, nitrate, sulfate, carbonate, cyanide, oxalate, thiocyanate, isocyanate, isothiocyanate, perchlorate, an alkanesulfonate such as methanesulfonate, an arylenesulfonate such as p-toluenesulfonate, trifluoromethanesulfonate (triflate) and C1-4 carboxylate. Chloride ion is especially preferred.
The metal cyanide catalyst is completed with a complexing agent that contains a hydrolyzable silane coupling group. By xe2x80x9ccomplexedxe2x80x9d, it is meant that the complexing agent becomes associated with the metal cyanide catalyst. The nature of the complexing is not fully understood, and may be due to a combination of factors. The completing may be due to the formation of a coordinate bond between a heteroatom on a functional group of the complexing agent and one or more of the metal ions (M, M1, M2, M3) of the metal cyanide catalyst. Another explanation of the complexing is that it is due to the complexing agent occupying vacancies within the crystalline structure of the metal cyanide, or that it otherwise is occluded within or bound into the crystalline lattice. However, it is not intended to limit this invention to any particular complexing mechanism.
The complexing agent has at least one hydrolyzable silane group that is linked to a group having at least one functional moiety through which the complexing agent can be complexed with the metal catalyst. The functional moiety advantageously contains at least one heteroatom that is preferably selected from oxygen, nitrogen, phosphorous, and sulfur. The heteroatom is most preferably oxygen. The functional moiety can be, for example, a sulfide, a sulfoxide, a sulfone, a phosphonate, a urethane, a urea, an amide, a nitrile, an alcohol, an aldehyde, a ketone, an ether or an ester group. Preferred functional groups include alcohols and ethers, or a combination of these.
Thus, preferred complexing agents can be represented as having the general structure

where D is a heteroatom containing group as described above, k is a positive number, s is zero or one, each R4 is independently hydrogen or an alkyl, aryl or alkoxyl group that may be substituted, R1 is a hydrolyzable group and R2 and R3 are groups that may be hydrolyzable or nonhydrolyzable. One or both of R2 and R3 may be another xe2x80x94Osxe2x80x94(C(R4)2)kxe2x80x94D linkage. Similarly, D may contain another xe2x80x94(C(R4)2)kxe2x80x94Osxe2x80x94Si(R1R2R3) group. Preferably at least one of R2 and R3 are hydrolyzable and more preferably both R2 and R3 are hydrolyzable. Preferred hydrolyzable groups include halogen, particularly chlorine, C1-8 alkoxyl, or substituted alkoxyl. R1 is preferably chloro, methoxy or ethoxy, as is at least one of R2 and R3. When s is one, the nature of the Sixe2x80x94Oxe2x80x94(C(R4)2)kxe2x80x94D linkage is such that the oxygen-silicon bond is substantially less susceptible to hydrolysis than R1 (and R2 and R3 when they are hydrolyzable). This permits selective hydrolysis of the R1 (and R2 and R3 groups when hydrolyzable) without substantial hydrolysis of the Dxe2x80x94C(R4)2)kxe2x80x94Oxe2x80x94 group. k is preferably 1-500, more preferably 1-10. s is preferably zero in all cases.
One preferred class of groups D is those having polyether segments. Polyether segments of particular interest are derived from ethylene oxide, propylene oxide, butylene oxide, or mixtures of two or more of these, and have a weight (number average) of from about 100 daltons, preferably from about 200 daltons, to about 8000 daltons, preferably to about 3000 daltons, more preferably to about 2000 daltons. Some complexing agents of this type are represented as:
R1R2R3Si(CH2)i(OR5)jOR6
wherein i is zero or a positive number, j is a positive number, R5 is an alkylene group which may be substituted and R6 is hydrogen, an organic group, or a xe2x80x94(CH2)iSiR1R2R3 group. The OR5 groups are preferably residues from polymerizing ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, tetramethylene oxide or mixtures of two or more thereof. R6 is preferably a C1-4 straight chain or branched alkyl group or a xe2x80x94(CH2)iSiR1R2R3 group. j is from 1 to about 200, preferably from about 5 to about 100, more preferably from about 5 to about 50. i is preferably from about 1 to about 12, more preferably from about 1 to about 4. Especially preferred complexing agents of this type are those in which i is about 1-4, the OR5 groups are residues of ethylene oxide, propylene oxide, 1,2-butylene oxide or tetramethylene oxide, and j is about 5 to about 50, R6 is C1-4 alkyl or xe2x80x94(CH2)iSiR1R2R3 (where i is again about 1-4) and R1, R2 and R3 are all methoxy or ethoxy groups.
Other preferred complexing agents include polyether segments that are connected to the terminal xe2x80x94(C(R4)2)kxe2x80x94Osxe2x80x94SiR1R2R3 group(s) through a linking group such as a urethane, urea or similar group. For example, a urethane-linked complexing agent can be prepared in the reaction of an isocyanate-functional silane compound with a hydroxyl-terminated polyether. The isocyanate group is preferably bound to the silicon atom through a non-hydrolyzable linkage, and the silicon atom is bound to groups R1, R2 and R3 as described before. Thus, suitable isocyanate-functional silane compounds include those represented by the structure OCNxe2x80x94Gxe2x80x94(C(R4)2)kSiR1R2R3 where k, R1, R2, R3 and R4 are as previously defined and G is a chemical bond or a linking group. The isocyanate-functional silane compound can be reacted with a hydroxyl- or amine-functional polyether to produce the desired silane-functional complexing agent. If desired, the hydroxyl- or amine-functional polyether may contain more than one isocyanate-reactive group, so that multiple xe2x80x94(C(R4)2)kSiRR2R3 groups can be introduced onto the complexing agent. The polyether advantageously has a molecular weight of about 100 to about 8000, preferably about 2500-4000, more preferably about 300-2500, and may be, for example, a polymer of ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, tetramethylene oxide or mixtures of two or more thereof.
Another way to produce a complexing agent having urethane or urea linking groups is to react a hydroxyl- or amine-functional silane compound with a polyether that contains one or more terminal isocyanate groups. The hydroxyl or amine groups preferably are bound to the silicon atom through a non-hydrolyzable linkage, and the silicon atom is bound to groups R1, R2 and R3 as before. Thus, suitable hydroxyl- or amine-functional silane compounds include those represented by the structures HOxe2x80x94Gxe2x80x94(C(R4)2)kSiR1R2R3 and HR4Nxe2x80x94Gxe2x80x94(C(R4)2)kSiR1R2R3, where k, R1, R2, R3, R4 and G are as previously defined. Polyethers having terminal isocyanate groups are easily prepared by reacting a hydroxyl or amine-terminated polyether with at least a stoichiometric quantity of a di- or polyisocyanate. Suitable di- or polyisocyanates include aromatic, aliphatic and cycloaliphatic types, including diphenylmethane diisocyanate, polymethylene polyphenylene polyisocyanates, toluene diisocyanate, H12MDI, isophorone diisocyanate, 1,6-hexane diisocyanate, and the like. As before, the starting polyether advantageously has a molecular weight of about 100 to about 8000, preferably about 2500-4000, more preferably about 300-2500, and may be, for example, a polymer of ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, tetramethylene oxide or mixtures of two or more thereof.
Another preferred type of complexing agent is a reaction product of an epoxy-functional silane and an alcohol. The epoxy group preferably is bound to the silicon atom through a non-hydrolyzable linkage, and the silicon atom is bound to groups R1, R2 and R3 as before. Thus, suitable epoxy-functional silane compounds include those represented by the structure Epxe2x80x94Gxe2x80x94(C(R4)2)kSiR1R2R3, where k, R1, R2, R3 R4 and G are as previously defined and Ep represents an epoxy group. Suitable alcohols include aliphatic alcohols having from about 1 to about 20 carbon atoms or more, and also include hydroxyl-terminated ethers and polyethers, such as those described before. Complexing agents of this type are conveniently prepared by reacting the epoxy-functional silane compound with the alcohol, typically in the presence of heat and a suitable catalyst such as boron trifluoride, and under conditions such that the R1, R2 and R3 groups are not hydrolyzed.
Thus, the complexed metal cyanide catalyst can be described as being represented by the general formula
Mb[M1(CN)r(X)t]c[M2(X)6]d.zL.nM3xAy
where L represents the silane-functional complexing agent and z is a positive number representing the relative quantity of complexed L molecules. A quantity of water or additional complexing agent may also be bound into the complex. Among the catalysts of particular interest are:
Zinc hexacyanocobaltate.zL.nZnCl2;
Zn[Co(CN)5NO].zL.nZnCl2;
Zns[Co(CN)6]o[Fe(CN)5NO]p.zL.nZnCl2 (o, p=positive numbers, s=1.5o+p);
Zns[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q. zL.nZnCl2 (o, p, q=positive numbers, s=1.5(o+p)+q);
Zinc hexacyanocobaltate.zL.nLaCl3;
Zn[Co(CN)5NO].zL.nLaCl3;
Zn[Co(CN)6]o[Fe(CN)5NO]p.zL.nLaCl3 (o, p=positive numbers, s=1.5o+p);
Zns[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q. zL.nLaCl3 (o, p, q=positive numbers,
s=1.5(o+p)+q);
Zinc hexacyanocobaltate.zL.nCrCl3;
Zn[Co(CN)5NO].zL.nCrCl3;
Zns[Co(CN)6]o[Fe(CN)5NO]p.zL.nCrCl3 (o, p=positive numbers, s=1.5o+p);
Zns[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q. zL.nCrCl3 (o, p, q=positive numbers,
s=1.5(o+p)+q);
Magnesium hexacyanocobaltate.zL.nZnCl2;
Mg[Co(CN)5NO].zL.nZnCl2;
Mgs[Co(CN)6]o[Fe(CN)5NO]p.zL.nZnCl2 (o, p=positive numbers, s=1.5o+p);
Mgs[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.nZnCl2 (o, p, q=positive numbers, s=1.5(o+p)+q);
Magnesium hexacyanocobaltate.zL.nLaCl3;
Mg[Co(CN)5NO].zL.nLaCl3;
Mgs[Co(CN)6]0[Fe(CN)5NO]p.zL.nLaCl3 (o, p=positive numbers, s=1.5o+p);
Mgs[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.nLaCl3 (o, p, q=positive numbers, s=1.5(o+p)+q);
Magnesium hexacyanocobaltate.zL.nCrCl3;
Mg[Co(CN)5NO].zL.nCrCl3;
Mgs[Co(CN)6]o[Fe(CN)5NO]p.zL.nCrCl3 (o, p=positive numbers, s=1.5o+p);
Mgs[Co(CN)6]o[Co(NO2)6]p[Fe(CN)5NO]q.zL.nCrCl3 (o, p, q=positive numbers, s=1.5(o+p)+q);
as well as the various complexes such as are described at column 3 of U.S. Pat. No. 3,404,109, incorporated herein by reference.
There are several convenient methods by which the silane-functional complexing agent can be complexed with the metal cyanide catalyst. In general, these processes include the steps of precipitating the metal cyanide catalyst from solutions of certain soluble metal salts and a soluble metal cyanide compound, and contacting the precipitate with the silane-functional complexing agent. The contacting with the complexing agent can be done during or after the initial precipitation of the metal cyanide catalyst. In addition, the silane-functional complexing agent can be formed in situ after the precipitation of the metal cyanide catalyst, as described below.
Aqueous preparation techniques can also be used, particularly when the silane-functional complexing agent is water miscible.
A convenient method is to precipitate the metal cyanide catalyst from a solution of the starting materials in an organic compound, in the presence of the silane-functional complexing agent. In this method, a solution or dispersion of a compound is mixed with a solution or dispersion of a metal salt. The solvent or dispersant includes an organic compound as described below. The soluble metal cyanide compound is represented by the general formula Hw[M1(CN)r(X)t], in which M1, X, r and t are as described before and w equals the absolute value of the [M1(CN)r(X)t] group. If desired, a solution of a compound of the general formula HwM2(X)6 may be included, either as part of the soluble metal cyanide compound solution or as a separate solution.
The organic compound is one that meets several requirements. First, it does not react with the soluble metal cyanide compound or any HwM2(X)6 compounds that may be present. In addition, it does not react with the metal salt. It is not a solvent for the metal cyanide catalyst complex that is formed in the reaction of the metal salt and the soluble metal cyanide compound. Preferably, the organic compound is a solvent for the soluble metal cyanide compound and any HwM2(X)6 compounds that may be used. In addition, the organic compound preferably is miscible with the silane-functional complexing agent. Even more preferably, the organic compound is relatively low boiling or otherwise easily separated from the silane-functional complexing agent. A preferred organic compound is methanol.
In the organic solution method just described, it is preferred to minimize or even eliminate water during formation of the DMC complex.
A solution of the metal cyanide compound in the organic compound can be prepared in several ways. In one preparation technique, an aqueous solution of the corresponding alkali metal cyanide salt (i.e., Bw[M1(CN)r(X)t], where B represents an alkali metal ion) is formed. This may be done at an elevated temperature if necessary to dissolve the metal cyanide salt. The aqueous solution is mixed with a stoichiometric excess of a concentrated mineral acid of the form HdJ, where J is an anion that forms an insoluble salt with B and d is the absolute value of the valence of J. Common mineral acids such as sulfuric acid and hydrochloric acid are preferred. Sulfuric acid is preferably used at a 75% or higher concentration. Hydrochloric acid is preferably used at a 30% or higher concentration, preferably about a 37% concentration. The salt of B and J precipitates, leaving the desired soluble metal cyanide compound Hw[M1(CN)r(X)t] in aqueous solution. The organic compound is then added, usually with stirring, preferably at a slightly elevated temperature in order to maintain the Hw[M1(CN)r(X)t] compound in solution. Because the salt of B and J is usually hygroscopic, a significant portion of the water is removed from the solution with the salt. The salt is easily separated from the supernatant liquid by filtration, centrifuging or other solid-liquid separation technique. If desired, the salt may be washed with additional quantities of the organic compound in order to recover any occluded Hw[M1(CN)r(X)t] compound.
A second method for preparing the solution of the soluble metal cyanide compound is to first form a slurry of the corresponding alkali metal cyanide salt (i.e., Bw[M1(CN)r(X)t]), in a mixture of the organic compound and a stoichiometric excess of a mineral acid, preferably hydrochloric acid. The hydrochloric acid can be supplied in various ways, such as by adding concentrated aqueous HCl, introducing gaseous HCl into the organic compound, or by adding a solution of HCl in an appropriate solvent (such as diethyl ether or isopropanol). An alkali metal salt of the acid forms and precipitates from the solution, leaving the desired Hw[M1(CN)r(X)t] compound dissolved in the organic compound. The precipitate is separated and if desired washed, as before.
A third convenient method of preparing the solution of the soluble metal cyanide compound is by ion exchange. An aqueous solution of the corresponding alkali metal salt (i.e., Bw[M1(CNr(X)t]) is eluted through a cation exchange resin or membrane which is originally in the hydrogen (H+) form. Sufficient resin is used to provide an excess of H+ ions. Suitable ion exchange resins include commonly available gel or macroporous, crosslinked polystyrene cation exchange resins, such as those sold by The Dow Chemical Company under the trade names DOWEX(copyright) MSC-1, DOWEX(copyright) 50WX4, as well as AMBERLYST(copyright) 15 ion exchange resin, sold by Rohm and Haas. The column is typically eluted with water until the desired soluble metal cyanide compound is recovered. The water is removed from the eluent, yielding the desired soluble metal cyanide compound as solid precipitate. This precipitate is then dissolved or dispersed in the organic compound. If desired, a small amount of water may be left in the soluble metal cyanide compound when it is mixed with the organic compound.
Other ion exchange methods for preparing the solution are described by F. Hein et al., Z. Anorg. Allg. Chem. 270, 45 (1952) and A Ludi et al, Helv. Chem. Acta 50, 2035 (1967). Yet other methods are described by Klemm et aL, Z. Anorg. Allg. Chem. 308, 179 (1961) and in the Handbook of Preparative Inorganic Chemistry, G. Brauer, Ed., Ferdinand Enke Verlag, Stuttgart, 1981.
The HwM2(X)6 compound can be made in an analogous way.
The solution of the metal salt usually can be prepared by directly dissolving the metal salt into an organic compound. The organic compound is as described above. In this solution, the organic compound is preferably the same as used in the soluble metal cyanide compound solution. If a different organic compound is used, it is preferably miscible with that used in the soluble metal cyanide compound solution.
The solutions are mixed in proportions such that an excess of the metal salt is provided, based on the amount of soluble metal cyanide compound. Preferably about 1.5 to about 4, more preferably from about 2 to about 3 moles of metal ion (M) are delivered per mole of M1(CN)r(X)t ion (or combined moles of M1(CN)r(X)t and M2(X)6 ions, when M2(X)6 ions are present). It is also preferred that the mixing be done with agitation. Agitation is preferably continued for a period after the mixing is completed. The metal cyanide catalyst, Mb[M1(CN)r(X)t]c[M2(X)6]d, precipitates and forms a fine dispersion in the organic compound.
The silane-functional compound is conveniently introduced into the complex by including it in one of the starting solutions or by adding it to the resulting dispersion, preferably immediately after the starting solutions are mixed. Less preferably, the silane-functional complexing agent (or solution thereof in a non-aqueous solvent) can be used to wash the precipitated metal cyanide catalyst. The silane-functional complexing agent can also be formed in-situ as described more below.
If desired, other complexing agents can be used in addition to the silane-functional complexing agent. If used, the additional complexing agent can be added in the same manner as the silane-functional complexing agent. A great number of complexing agents are potentially useful, although catalyst activity may vary according to the selection of a particular complexing agent. Examples of such complexing agents include alcohols, aldehydes, ketones, ethers, amides, nitrites, sulfides, and the like.
Preferred additional complexing agents are t-butanol, 1-t-butoxy-2-propanol, polyether polyols having an equivalent weight of about 75-350 and dialkyl ethers of alkylene and polyalkylene glycols. Especially preferred complexing agents are t-butanol, 1-t-butoxy-2-propanol, polyether polyols having an equivalent weight of 125-250 and a dimethyl ether of mono-, di- or triethylene glycol. t-Butanol and glyme (1,2-dimethoxy ethane) are especially preferred.
In addition, a binder as described further below can be added with the silane-functional complexing agent.
The metal cyanide catalyst/silane-functional complexing agent dispersion (containing additional complexing agent and/or binder, if desired) is conveniently formed into a shaped polymer by casting, spraying or similar methods, followed by curing. If desired, the dispersion may include a solvent, such as the organic compounds discussed above, in order to reduce viscosity and facilitate the shaping process. This solvent is also most advantageously removed during the curing process.
Curing is performed by contacting the dispersion with enough water to hydrolyze the R1 groups and those of the R2 and R3 groups that are hydrolyzable. While not intending to be bound by any theory, it is believed that the hydrolyzable groups initially undergo hydrolysis to Sixe2x80x94OH groups. Next, these Sixe2x80x94OH undergo hydrogen bonding to each other (and the surface of certain supports, if present). The Sixe2x80x94OH groups then condense (with loss of water) to create Sixe2x80x94Oxe2x80x94Si bonds between silane-functional complexing agent molecules or Sixe2x80x94O-surface bonds. Thus, in this invention, the term xe2x80x9corganosiliconexe2x80x9d polymer is used in a broad sense to include polymers having alternating silicon and oxygen atoms, and in which the silicon atoms are substituted with organic radicals. At least some of the silicon atoms that are substituted with organic radicals are derived from the silane-functional ligand.
This xe2x80x9ccuringxe2x80x9d process can be done at ambient or elevated temperatures. The rate and degree of curing is controlled through the rate at which water is removed from the mixture. The water is typically added prior to casting or spraying the dispersion, preferably during or more preferably after precipitating the catalyst. As a certain amount of water is present in the reagent solutions, it may not be necessary to provide additional water. Alternately, the water for hydrolysis can be provided as intrinsic water contained within a support, or may applied to the dispersion after it is cast or sprayed.
The cured polymer advantageously contains from about 1, preferably from about 5, more preferably from about 10, especially from about 20 weight percent, to about 75, preferably to about 65, more preferably to about 50 weight percent of metal cyanide catalyst. In this context, the weight of the metal cyanide catalyst is considered to be the weight of the Mb[M1(CN)r(X)t]c[M2(X)6]d.nM3xAy material, exclusive of any associated water or complexing agent compounds.
A supported catalyst is easily prepared by forming the polymer onto the surface of a suitable support. Supports can be organic or, preferably, inorganic materials. Organic supports include polyacrylate or styrene copolymer particles, especially when crosslinked. Inorganic supports include, for example, oxides, carbides, nitrides or metals. Examples of oxides are oxides of metals of groups IIA to IVA and IB to VIIIB, especially alumina and silica. Examples of carbides include silicon carbide, boron carbide and tungsten carbide. Examples of nitrides include boron nitride, silicon nitride or aluminum nitride. Metal supports include metals and metal alloys such as steel, aluminum, noble metals, nickel, stainless steel, titanium, tantalum and canthal. Especially preferred supports are those that can form an Sixe2x80x94Oxe2x80x94X bond to the silane-functional completing agent, where X refers to an atom bound onto the support. Some supports of particular interest include silica gel (especially in particulate form, such as from about 60-200 mesh (U.S. Sieve)), silica chips (such as, e.g. from about 6 to about 200 mesh), alumina particulates or spheres, porous alumina spheres or particulates, polyacrylate or styrene/divinylbenzene copolymer particles, catalyst substrate spheres, and the like. Particulate supports provide the advantages of having large surface areas and being easily separated from a polyether made using the supported catalyst. However, the support may also be the interior surface of a reaction vessel such as a pipe or tubular reactor, a screen, honeycomb or other structure inserted within the reaction vessel, or the like.
To form a supported catalyst, the dispersion containing the precipitated catalyst and silane-functional completing agent is subjected to hydrolysis conditions as described before in the presence of the support.
Supported catalysts according to the invention advantageously contain from about 1, preferably from about 3, more preferably from about 5, especially from about 20 weight percent, to about 50, preferably to about 25, more preferably to about 15 weight percent of metal cyanide catalyst. As before, the weight of the metal cyanide catalyst is considered to be the weight of the Mb[M1(CN)r(X)t]c[M2(X)6]d.nM3xAy material, exclusive of any associated water or complexing agent compounds.
If desired, a binder can be present when the silane-functional completing agent is hydrolyzed to form the polymer. This is especially desirable when the polymer is formed onto a support. Suitable binders include, for example, esters of silicic acid (such as a tetra alkyl orthosilicate), borates, aluminates (especially aluminum alkosides), titanates (especially titanium alkoxides) and/or zirconates. Esters of silicic acid that do not have a heteroatom-containing functional group (other than the silane group itself) are preferred, as these are capable of forming Sixe2x80x94Oxe2x80x94Si bonds with the silane-functional complexing agent to form a copolymer. Particularly preferred binders are tetraethyl orthosilicate and tetramethyl orthosilicate.
It is possible in some instances to form the silane-functional complexing agent in situ in the presence of the precipitated catalyst. For example, a silane-functional complexing agent prepared by reacting an isocyanate-terminated polyether and a hydroxyl-terminated silane can be created by precipitating the catalyst in the presence of the isocyanate-terminated polyether. The hydroxyl-terminated silane compound can be added to the resulting dispersion (together with a suitable catalyst if desired) and caused to react with the isocyanate-terminated polyether to form the silane-functional complexing agent in the presence of the precipitated catalyst. This reaction can be conducted simultaneously with the curing of the polymer, so that the formation of the silane-functional complexing agent and the polymer is performed in a single step. As before, this can be done in the presence of a suitable support.
In analogous manner, the catalyst can be precipitated in the presence of an alcohol, and the resulting dispersion mixed with an epoxy-functional silane or an isocyanate-functional silane that can be reacted with the alcohol to form the silane-functional completing agent in situ. However, water should not be present when an isocyanate-functional silane is used in this manner, in order to avoid formation of urea compounds and generation of carbon dioxide.
The catalyst complex of the invention is used to polymerize alkylene oxides to make polyethers. In general, the process includes mixing a catalytically effective amount of the catalyst with an alkylene oxide under polymerization conditions, and allowing the polymerization to proceed until the supply of alkylene oxide is essentially exhausted. The concentration of the catalyst is selected to polymerize the alkylene oxide at a desired rate or within a desired period of time. An amount of polymer or supported catalyst as described above sufficient to provide from about 5 to about 10,000 parts by weight metal cyanide catalyst (calculated as Mb[M1(CNr(X)t]c[M2(X)6]d.nM3xAy, exclusive of supports and any associated water or complexing agent compounds) per million parts combined weight of alkylene oxide and initiator and comonomers, if present. More preferred catalyst levels are from about 20, especially from about 30, to about 5000, more preferably about 1000 ppm, even more preferably about 100 ppm, on the same basis.
For making high molecular weight monofunctional polyethers, it is not necessary to include an initiator compound. However, to control molecular weight, impart a desired functionality (number of hydroxyl groups/molecule) or a desired terminal functional group, an initiator compound as described before is preferably mixed with the catalyst complex at the beginning of the reaction. Suitable initiator compounds include monoalcohols such methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, 1-t-butoxy-2-propanol, octanol, octadecanol, 3-butyn-1-ol, 3-butene-1-ol, propargyl alcohol, 2-methyl-2-propanol, 2-methyl-3-butyn-2-ol, 2-methyl-3-butene-2-ol, 3-butyn-1-ol, 3-butene-1-ol and the like. The suitable monoalcohol initiator compounds include halogenated alcohols such as 2-chloroethanol, 2-bromoethanol, 2-chloro-1-propanol, 3-chloro-1-propanol, 3-bromo-1-propanol, 1,3-dichloro-2-propanol, 1-chloro-2-methyl-2-propanol as well as nitroalcohols, keto-alcohols, ester-alcohols, cyanoalcohols, and other inertly substituted alcohols. Suitable polyalcohol initiators include ethylene glycol, propylene glycol, glycerine, 1,1,1-trimethylol propane, 1,1,1-trimethylol ethane, 1,2,3-trihydroxybutane, pentaerythritol, xylitol, arabitol, mannitol, 2,5-dimethyl-3-hexyn-2,5-diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, sucrose, sorbitol, alkyl glucosides such a methyl glucoside and ethyl glucoside and the like. Low molecular weight polyether polyols, particular those having an equivalent weight of about 350 or less, more preferably about 125-250, are also useful initiator compounds.
Among the alkylene oxides that can be polymerized with the catalyst complex of the invention are ethylene oxide, propylene oxide, 1,2-butylene oxide, styrene oxide, and mixtures thereof. Various alkylene oxides can be polymerized sequentially to make block copolymers. More preferably, the alkylene oxide is propylene oxide or a mixture of propylene oxide and ethylene oxide and/or butylene oxide. Especially preferred are propylene oxide along or a mixture of at least 75 weight % propylene oxide and up to about 25 weight % ethylene oxide.
In addition, monomers that will copolymerize with the alkylene oxide in the presence of the catalyst complex can be used to prepare modified polyether polyols. Such comonomers include oxetanes as described in U.S. Pat. Nos. 3,278,457 and 3,404,109, and anhydrides as described in U.S. Pat. Nos. 5,145,883 and 3,538,043, which yield polyethers and polyester or polyetherester polyols, respectively. Hydroxyalkanoates such as lactic acid, 3-hydroxybutyrate, 3-hydroxyvalerate (and their dimers), lactones and carbon dioxide are examples of other suitable monomers that can be polymerized with the catalyst of the invention.
The polymerization reaction typically proceeds well at temperatures from about 25 to about 150xc2x0 C., preferably from about 80-130xc2x0 C. A convenient polymerization technique involves mixing the catalyst complex and initiator, and pressuring the reactor with the alkylene oxide. After a short induction period, polymerization proceeds, as indicated by a loss of pressure in the reactor. Once the polymerization has begun, additional alkylene oxide is conveniently fed to the reactor on demand, until enough alkylene oxide has been added to produce a polymer of the desired equivalent weight.
Another convenient polymerization technique is a continuous method. In such continuous processes, an initiator is continuously fed into a continuous reactor, such as a continuously stirred tank reactor (CSTR) or a tubular reactor that contains the catalyst. A feed of alkylene oxide is introduced into the reactor and the product continuously removed.
The catalyst of this invention is easily separated from the product polyether by any convenient solid-liquid separation, including simple filtration and centrifuging. The recovered catalyst can be re-used in further polymerization reactions.
The recovered catalyst may be washed one or more times, preferably multiple times, with water or preferably an organic solvent such as methanol, and then dried prior to being re-used. If the surface of the catalyst becomes fouled or coated with polymer, the catalyst may be washed or treated to remove the fouling or polymer coating.
The catalyst of this invention is especially useful in making propylene oxide homopolymers and random copolymers of propylene oxide and up to about 15 weight percent ethylene oxide (based on all monomers). The polymers of particular interest have a hydroxyl equivalent weight of from about 800, preferably from about 1000, to about 5000, preferably to about 4000, more preferably to about 2500, and unsaturation of no more than 0.02 meq/g, preferably no more than about 0.01 meq/g.
The product polymer may have various uses, depending on its molecular weight, equivalent weight, functionality and the presence of any functional groups. Polyether polyols so made are useful as raw materials for making polyurethanes. Polyethers can also be used as surfactants, hydraulic fluids, as raw materials for making surfactants and as starting materials for making aminated polyethers, among other uses.